AUSTIN, TEXAS — A preliminary analysis of dog paddling has already sunk the old idea that swimming dogs just trot in water.

In a trot, a front paw (or hoof or foot) rises and falls in sync with the hind paw on the opposite side, explained Frank Fish of West Chester University in Pennsylvania. Although dog paddling had never been analyzed, he said, even he on occasion had described it as trotting in water.

Underwater videos of the churning paws of six breeds of dog, however, revealed motions more like running than trotting, Fish reported January 5 at the annual meeting of the Society for Integrative and Comparative Biology. Diagonally opposite paws didn’t stroke with trotlike synchrony, he and a colleague found. Instead, the four legs perform strokes in a pattern that’s more complex, and more of a type of run than a trot. The gait is also remarkably consistent across breeds, from galumphing Newfoundlands to a small Jack Russell terrier.

Studying terrestrial mammals’ inefficient swimming offers a way to reach back in evolutionary history to understand the pressures that might have driven four-legged land animals struggling in water to streamline into today’s marine mammals. “Dogs are beautiful for this,” Fish said.

For the study, eight dogs, including a German shepherd, a Labrador retriever and Fish’s own Nova Scotia duck tolling retriever, paddled back and forth in a swimming pool or veterinary water-therapy tanks. Meanwhile, Fish, submerged in scuba gear, filmed their legs. The Yorkshire terrier recruited for the study was small enough to paddle in a long aquarium in Fish’s lab.

A dog paddle is inefficient, but the gait has its nuances. Dogs extend their legs during the power stroke of sweeping down and back. As they bring that leg forward again, Fish found, they reduce drag in the water by slowing the leg’s motion and by tucking it close to the body.

Dogs may not be elegant swimmers, but some legged animals manage quite well without fins, said Jeannette Yen, an aquatic chemical ecologist at Georgia Tech in Atlanta. Tiny krill, crustaceans that are widespread in the world’s oceans, swim marathon migrations with their five pairs of legs beautifully coordinated, Yen said.

Fish has already investigated other legged swimmers, but he has no plans to attempt to study cats swimming.

BEAUTIFUL SWIMMER A Nova Scotia duck tolling retriever demonstrates her dog paddle at full and then half speed for the sake of gait science. A new study finds that a dog’s swimming stroke is more akin to a run than a trot.Credit: Courtesy of F. Fish.